Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $192.50   10.755%   $213.2034   $213.20   $213.20   $213.20  
  Purchase #2 $173.46   13.744%   $197.3003   $197.30   $197.30   $197.30  
  Purchase #3 $183.77   8.639%   $199.6459   $199.65   $199.65   $199.60  
  Purchase #4 $193.35   12.687%   $217.8803   $217.88   $217.90   $217.90  
  Purchase #5 $239.90   11.517%   $267.5293   $267.53   $267.55   $267.50  
  Purchase #6 $201.92   4.278%   $210.5581   $210.56   $210.55   $210.60  
  Purchase #7 $203.82   12.569%   $229.4381   $229.44   $229.45   $229.40  
  7 purchase totals = $1,388.72       $1,535.5554   $1,535.56   $1,535.60   $1,535.50